$-4hj + 9i + 10j - 1 = -9i + j + 7$ Solve for $h$.
Combine constant terms on the right. $-4hj + 9i + 10j - {1} = -9i + j + {7}$ $-4hj + 9i + 10j = -9i + j + {8}$ Combine $j$ terms on the right. $-4hj + 9i + {10j} = -9i + {j} + 8$ $-4hj + 9i = -9i - {9j} + 8$ Combine $i$ terms on the right. $-4hj + {9i} = -{9i} - 9j + 8$ $-4hj = -{18i} - 9j + 8$ Isolate $h$ $-{4}h{j} = -18i - 9j + 8$ $h = \dfrac{ -18i - 9j + 8 }{ -{4j} }$ Swap the signs so the denominator isn't negative. $h = \dfrac{ {18}i + {9}j - {8} }{ {4j} }$